Electric Drive Vehicle Control System

ABSTRACT

Electronic control systems and related control methods for controlling electric drive motors for propelling a vehicle and electric auxiliary motors for performing work. The apparatus is shown in use with a vehicle that includes a mowing deck. Features of the control systems allow for safe and efficient use of the vehicle. These features include a power take-off timeout, automatic fail-safe brake (parking), and customized drive characteristics.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/209,074, filed Sep. 11, 2008, which claimspriority to U.S. Provisional Patent Application No. 60/971,419, filed onSep. 11, 2007, all of which are incorporated by reference herein in itsentirety.

TECHNICAL FIELD

This application is generally related to electrically powered vehicles,and more particularly to control systems, methods and processes forelectric drive mechanisms of electrically powered vehicles, such as, forexample, utility vehicles.

BACKGROUND OF THE INVENTION

Utility vehicles, such as, for example, lawn tractors, have generallyrelied upon internal combustion engines as the prime mover transferringpower through mechanical linkages (gearing or belts), hydrostaticdrive(s), continuously variable transmissions (CVTs), or other similardevices to propel the vehicle. However, manufacturers of these vehicles,especially lawn tractors used for lawn mowing, are under continuouslyincreasing pressure to reduce environmental pollution caused by vehicleemissions, as well as fluid leaks and noise from the hydrostatictransmission or engine. Hence, utility vehicles utilizingelectrically-powered systems have become a primary focus to addressthese and other issues with combustion-engine type vehicles.

SUMMARY OF THE INVENTION

The present invention comprises systems, methods and processes forelectric drive mechanisms of electrically powered vehicles, such as, forexample, utility vehicles. In a particular embodiment, electroniccontrol processes are utilized to control electronic traction andauxiliary drive systems, such as a mower deck drive mechanism. In anembodiment incorporating a mowing deck, the control processes control,among other things, vehicle travel and mower deck cutting blade speed.In such an embodiment, the electric motors receive signals from thecontrol system of the vehicle in accordance with programmed processes tocontrol the transmission driving speed and power take-off (PTO), and,hence, the mower deck cutting blade operation. The systems, methods andprocesses of the present invention have many other applications innumerous types of electrically powered vehicles.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forth one ormore illustrative embodiments that are indicative of the various ways inwhich the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a vehicle incorporating an embodiment of anelectrically powered vehicle with an embodiment of a typical operatorcontrol panel in accordance with the principles of the presentinvention.

FIG. 2 is a block diagram illustrating an overview of the vehiclecontrol system in accordance with the principles of the presentinvention.

FIG. 3 is a bubble diagram of the various operating states of theelectronic traction control system shown in FIG. 2.

FIG. 4 is a bubble diagram of the various operating states of theelectronic mower deck drive control system shown in FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the present invention in accordance with itsprinciples. This description is not provided to limit the invention tothe embodiments described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiments describedherein, but also other embodiments that may come to mind in accordancewith these principles. The scope of the present invention is intended tocover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers, such as, for example, in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. Such labeling and drawing practices do not necessarilyimplicate an underlying substantive purpose. As stated above, thepresent specification is intended to be taken as a whole and interpretedin accordance with the principles of the present invention as taughtherein and understood by one of ordinary skill in the art. It shouldalso be noted that references herein to specific manufactured componentsmay be provided as preferred embodiments or exemplifications and shouldnot be construed as limiting. In each case, similar or equivalentcomponents from other manufacturers may be utilized as well.

FIG. 1 shows a vehicle 12 implementing one or more embodiments inaccordance with the principles of the present invention. While vehicle12 shown in FIG. 1 is a mowing vehicle, the principles of the presentinvention may be applied to other vehicles as well, such as, forexample, utility vehicles, tractors, or other vehicles incorporatingauxiliary systems (e.g., mower blades, augers, snow throwers, tillers,sweepers, spreaders, etc.) that can benefit from integrated control witha drive system. Vehicle 12 includes a power supply 13, a mower deck 14,a pair of driven wheels 18 and a pair of steered wheels 25. In analternate embodiment (not shown), a single steered wheel may be used. Inthe embodiment shown, vehicle 12 also includes an electric transaxle 10that drives a pair of output shafts or axles 16, which in turn drive apair of wheels 18 that provide motion to vehicle 12. It should be notedthat the use of the term wheel is intended to cover all types of wheels,as well as gears, linkages, or other mechanisms that may ultimatelytranslate into a traction implement, such as, for example, an innerwheel of a track arrangement on a track vehicle.

Vehicle 12 includes a plurality of systems to perform various functions,such as vehicle control system 50, which is illustrated separately inFIG. 2. A general overview of the interaction between control system 50and other portions of vehicle 12 is illustrated in the block diagram ofFIG. 2. Traction controller 51 controls transaxle 10 and, when certainoperational conditions are met, allows the operator of vehicle 12 toclose PTO switch 43 to energize or allow activation of one or morefunctional outputs of an auxiliary controller in the form of deckcontroller 52, which can drive a variety of auxiliary equipment such asmower deck 14 (illustrated), or in other embodiments, a snow thrower, atiller, sweeper brooms, or other implements. In the illustratedembodiment, traction controller 51 is an AC-0 inverter manufactured byZapi, Inc. of Cary, N.C. Controller terminal and pin identifiers, suchas A5, A6, B7, B8, etc., are shown for reference only. Other circuitarrangements/pin assignments are possible. Alternatively, many othertypes of processors, programmable logic controllers (PLCs), or the likecould be utilized in accordance with the principles of the presentinvention.

Referring again to FIGS. 1 and 2, control system 50 includes tractioncontroller 51 that receives signals from, and sends signals to, variousother portions of control system 50 and vehicle 12. Transaxle 10includes an electric motor 11 (which may be, for example, anasynchronous three-phase AC induction motor or any other electric motortype sufficient for driving a vehicle) that is drivingly attached togearing within transmission 17, thereby transmitting torque to axle oroutput shafts 16, which causes rotation of driven wheels 18. In analternate embodiment, vehicle 12 may include two transmissions, eachindependently driving one of a set of opposed axles, each having anassociated drive wheel, such as in a zero-turn vehicle arrangement. Inyet another embodiment, vehicle 12 may include two electric direct drivemotors, each independently driving one of a set of opposed wheelswithout transmissions, such as in a zero-turn vehicle arrangement. Theprinciples of the present invention apply to these types of arrangementsas well.

Referring once again to FIGS. 1 and 2, traction controller 51 of controlsystem 50 controls the speed and direction of vehicle 12. The speed oftransaxle 10 can be adjusted by regulating the voltage frequencysupplied to electric motor 11. Feedback used in the control of vehicle12 is provided to traction controller 51 by speed sensor 37 of electricmotor 11 on transaxle 10.

Speed sensor 37 of electric motor 11 may be a dual Hall Effect sensorthat can sense and signal both a change in acceleration and rotationdirection of electric motor 11. Feedback from speed sensor 37 enablesexecution of programming of desired characteristics of acceleration,deceleration, neutral, and change in direction via control software inconnection with traction controller 51. The flexibility of programmingallows features such as, for example, a panic stop ramped decelerationfunction, custom acceleration/deceleration curves, or other programmablefunctions to be implemented.

Electric motor 11 may be protected from damage by over-current andover-voltage sensors or circuitry (not shown) located in tractioncontroller 51. MOSFETs (metal-oxide-semiconductor field-effecttransistors) located within controller 51 are protected by thecontroller's capability to monitor current and temperature. Atemperature sensor 36 may be located in electric motor 11 to protectelectric motor 11 from overheating. Feedback from these sensors may beused to perform system checks, regulate vehicle speed, disable the PTO,initiate a controlled shutdown, sound or display a warning, or performother functions relating to the vehicle. Additionally, in a particularembodiment, vehicle 12 may be driven in a forward or reverse directionby operator control of accelerator pedal 40, which may be a “rockerstyle,” heel and toe operated pedal that includes one or more associatedor integrated switches to signal direction and a potentiometer (or othersignal-generating device) to signal desired speed to traction controller51. Alternatively, the potentiometer utilized in the accelerator pedal40 can be utilized to generate a signal representative of both speed anddirection. Optionally, a separate F-N-R (Forward-Neutral-Reverse) switchcould be employed, which is used in conjunction with a simpleaccelerator pedal that signals desired speed only. Such a switch can bemounted on dash 20. In yet another embodiment (not shown), two separatepedals could be used for forward and reverse directions of vehiclemovement. This option allows manufacturers flexibility in choosingtraditional operator controls or a different configuration. A wiringharness or assembly 54 may be used to electrically connect the variouselements of control system 50. Wiring harness 54 may be configured sothat wires carrying signals are grouped together and wires carryingpower and drive signals are grouped together with appropriate shieldingfor signal integrity.

As shown in FIGS. 1 and 2, power supply 13 is provided to operate one ormore systems of vehicle 12, including components of control system 50.In the embodiment shown, power supply 13 consists of four 12V batteriesproviding 48V power. Power is distributed from power supply 13, throughpower contactor 53, to traction controller 51. In the embodiment shown,power contactor 53 is a Model SW60 contactor manufactured by AlbrightInternational, Ltd. of Surbiton, UK (England). Power supply 13 is alsoin electrical communication with on-off key switch 23. With key switch23 in the ON position, and with the presence of power at a specifiedvoltage threshold from power supply 13, power contactor 53 enablestraction controller 51 after diagnostic checks verify that tractioncontroller 51 is ready to run.

Referring again to FIGS. 1 and 2, movement of rocker style acceleratorpedal 40 (or other accelerator mechanism) signals traction controller 51of an operator-directed acceleration or deceleration of vehicle 12 ineither the forward or reverse direction. The input signals fromaccelerator pedal 40 determine the direction and speed of operation oftransaxle 10.

As explained above, vehicle 12 includes operator interfaces, switches,sensors, and other components that interact within control system 50 toeffectuate control of vehicle 12. Brake pedal 32 of vehicle 12 actuatesa brake system located either as part of transaxle 10 or as a separatedevice or system. The brake system may be based on regenerative braking,mechanical braking, or a combination. Steering wheel 19 or othersteering mechanism or control interface facilitates turning of vehicle12 by mechanical, electro-mechanical, hydrostatic, or other knownmethods of controlling positioning of steered wheels 25. In theillustrated embodiment, vehicle dash 20 or an equivalent includes anindicator LED (light emitting diode) or lamp 22, vehicle key switch 23,PTO switch 43, cruise switch 42, reverse operating system (ROS) switch41, brake switch 30, emergency stop switch 31, battery gauge 21 and hourmeter 24. FIG. 2 illustrates an embodiment of some of these controls,switches, sensors and components in more detail.

The following description describes a representative array of elements.Some of these elements may be optional for a particular vehicleconfiguration. In other configurations, additional elements may bedesirable. For example, a speed sensor 37 or temperature sensor 36 maybe unnecessary in some applications. In another example, additionalsensors may be desired to improve operator satisfaction or safety. Suchsensors may include thermocouples, proximity aids, vehicle attitude orinclination sensors, and other devices relevant to the operation of atypical vehicle. Furthermore, activation of, for example, a vehicleattitude or inclination sensor may be used to initiate a secondaryfunction, such as transmission of an emergency signal to a remotereceiver in the event of a vehicle rollover.

In an embodiment, control system 50 controls three general categories offunctionality of vehicle 12: (1) diagnostics and start-up associatedwith traction controller 51 to enable control system 50 for vehicle 12,(2) operational parameters or constraints for traction controller 51during operation, and (3) operational parameters or constraints forother features of traction controller 51 and deck controller 52 systems.Each of these general categories is discussed below.

There are several control aspects related to starting and runningvehicle 12. Because vehicle 12 is accelerated electrically, adiagnostics routine is performed on the electronics prior to permittingvehicle 12 to be operated. If the battery charge does not meet theminimum threshold, traction controller 51 will prevent start-up.Referring to FIG. 2, when key switch 23 is rotated to the ON position,traction controller 51 performs an array of diagnostics. Once thediagnostics have successfully been completed, a relay permits actuationof power contactor 53. As will be noted in more detail later, tractioncontroller 51 continuously monitors a variety of conditions and has theability to shut down the system by way of disengaging power contactor53. Once power contactor 53 is engaged, functionality of the fail-safe,normally-closed brake 15 is checked. Part of this check involvesverifying the brake holding capacity at start-up to ensureserviceability. Traction controller 51 drives the electric motor 11 tothe required holding torque specification and monitors whether the drivewheels 18 move. If the check fails, the controller can be programmed toallow operation in a reduced power mode or disable the electric drivesystem. The controller can also be programmed to bypass the fail-safeholding torque check.

As the system continues performing diagnostics that will enable tractioncontroller 51 and mower deck controller 52, seat switch 34 is checked toverify operator presence. Functionality of traction controller 51 ischecked and the drive state is enabled. The neutral state of vehicle 12is verified. The inactive state of power take-off switch 43 and cruiseswitch 42 is also verified. The position of ROS switch 41 is checkedagainst the drive state of vehicle 12. After the diagnostic programpasses checks, LED indicator lamp 22 indicates a “No Error” state, andpower contactor 53 is switched on to enable propelling vehicle 12. In aparticular embodiment, other diagnostic options may be selectivelyincluded via software, such as, for example, limited or disabledfunctionality relative to battery capacity or state.

Referring again to FIGS. 1 and 2, when power contactor 53 is switchedon, traction controller 51 is enabled. Traction controller 51 receivessignals from various inputs of vehicle 12 that relate to motiveoperation of vehicle 12. Initially, a check for inputs from acceleratorpedal 40 is performed. If accelerator pedal 40 has been moved out of theneutral position (also referred to as PEDAL OFF in FIG. 3), fail-safebrake 15 is disengaged to allow the vehicle to travel the respectivespeed and direction indicated. Acceleration and decelerationcharacteristics can be programmed via software in connection withtraction controller 51, which allows selection of acceleration ordeceleration curves with different characteristics for greater operatorsatisfaction and control based on operator inputs or vehicle conditions.For example, deceleration curves may be programmed for a coast-to-stopfunction or for a panic stop function when encountering a sudden hazard.A panic-stop may be initiated by operator input or by object detectionsensor (not shown) input to traction controller 51. Other sensors orsystem diagnostics may also be used to initiate a system-controlledvehicle stop. The acceleration or deceleration curves can bepredetermined and stored in a memory associated with the controller, oroptionally can be customizable and programmed by a manufacturer(including original equipment manufacturers and authorized servicetechnicians) given certain safety constraints. These programmed curves,at the manufacturer's election, can be made selectable by an operator ofthe vehicle.

Once traction controller 51 is enabled, and when programmed safeoperating conditions are met, PTO switch 43 can be activated to runauxiliary or deck motors 27 and 28 of mower deck 14 (or other optionalattachment or implement). The current draw by drive motor 11 can beregulated for control. For example, the current draw can be regulatedmanually with the addition of an operator-manipulated potentiometer(e.g., knob, lever, or slide control—not shown). Optionally, the currentdraw can be automatically regulated via traction controller 51 to slowvehicle 12 if induced loads become high, such as when mowing thick ortall grass or when traveling up a steep grade, or if power consumptionexceeds programmed parameters. This can be accomplished by enablingcommunication between traction controller 51 and deck controller 52,such as via CAN (Controller Area Network) bus or other control unitconnection standard. Such regulation lowers power consumption, extendsbattery life between charges and optimizes operation levels to extendservice life. Other signals may be desirable to enable control system 50to provide safer and more effective operation of vehicle 12. Tractioncontroller 51 may provide an indication of the operating condition ofthe traction or deck drive systems by way of an indicator such as LED orindicator lamp 22 or by way of other operator interfaces which may bevisual, audible, or a combination of visual and audible.

The remaining control aspects of traction controller 51 relate tooperation of deck motors 27 and 28 associated with mower deck 14. Oncetraction controller 51 is enabled, the operator has the ability toactivate deck controller 52. Deck controller 52 drives mower deck motors27 and 28 which, in the embodiment shown, are controlled independentlyby two separate circuit boards (one for each motor) housed within deckcontroller 52. Operator actuation of PTO switch 43, when programmed safeoperating conditions are met, will cause deck controller 52 to powerright deck motor 27 and left deck motor 28, which drive the cuttingblades of mower deck 14. In a particular embodiment, deck motors 27 and28 are brushless DC (BLDC) motors, which each include Hall Effectsensors that provide feedback information to deck controller 52.Optionally, sensorless PMSMs (permanent magnet synchronous motors) maybe employed utilizing other feedback arrangements known in the art, suchas motor position and timing estimates based on software algorithms. Atemperature sensor (not shown) is also included in each deck motor toprovide feedback to deck controller 52 to prevent overheating of deckmotors 27 and 28. Additionally, over-current and over-voltage sensors(not shown) are included in deck controller 52 to prevent damage to deckmotors 27 and 28. Again, optionally, other feedback arrangements can beutilized, such as motor position and timing estimates, voltage andcurrent estimates, etc., based on software algorithms. In an alternateembodiment (not shown), feedback from sensors in deck motors 27 and 28and deck controller 52 can be integrated with feedback from sensorsproviding information to traction controller 51 and used to regulate thespeed of vehicle 12. This integration can be used to limit powerconsumption and proportionately adjust for the load each driveencounters with respect to available power. As noted above, this can beaccomplished by utilizing a CAN bus. Additionally, axle shafts 16 mayhave speed sensors (not shown) associated with them. Speed sensors maybe used for several purposes, such as, for example, determining theneutral position or neutral state of transaxle 10, which allows thecontroller to presume transaxle 10 is in the neutral position when theneutral position or state is sensed. Speed sensors associated with axleshafts 16 would, among other things, enhance the ability to establishthe non-rotating condition of axle shafts 16, thereby further definingthe neutral position. The controller system could automatically initiatea vehicle speed reduction in the mowing state and make furtheradjustments under increasing loads. This can be triggered alternativelyby current draw or temperature constraints.

According to another aspect, deck controller 52 allows for aprogrammable timeout if vehicle 12 is stopped for a set period of time.Other power conservation and safety features can be readily programmed,such as a multi-stage shutdown sequence to protect and manage powersupply 13 when the charge has deteriorated to specified levels.

In a particular embodiment, the first time the specified minimum voltagelevel is reached and sensed for a predetermined period (5 seconds, forexample), the deck motors 27 and 28 associated with deck 14 are disabledand a reduced vehicle speed is implemented to reduce the load on powersupply 13. If the voltage then draws down to the minimum voltage leveland is sensed for more than a. predetermined period a second time, thetraction drive speed is reduced again (to 20% of maximum, for example).If the minimum charge level is reached and sensed for a predeterminedperiod a third time, the traction drive may be disabled, stopping thevehicle. Optionally, the vehicle may enter a hibernation state whereintravel modes are disabled, but minimal power is still available toenergize, for example, a visual display, emergency lights, or anemergency signal transmitter while key switch 23 remains in the ONposition.

An alarm to remind the operator to recharge power supply 13 can beemployed at vehicle shutdown to help prevent deep battery discharge andprepare vehicle 12 for next use. A plug-in “smart” charger may be usedto charge power supply 13. This “smart” charger may be on-board vehicle12 or external to vehicle 12. Another optional feature is employment ofregenerative braking of the electric motor(s) to charge the system powersupply during braking or when the vehicle is coasting.

When attempting to move in reverse with a mower deck engaged, a reverseoperating system (ROS) typically stops the blades of the mower deck byremoving power from an electric clutch-brake or by killing the primemover to stop the vehicle. In the embodiment shown, closing ROS switch41 allows the operator to bypass this function to permit operation ofdeck motors 27 and 28 and associated mower blades when accelerator pedal40 is moved to a position indicating reverse travel of vehicle 12. ThisROS function is facilitated by the interaction between tractioncontroller 51 and deck controller 52. The ROS function allowsuninterrupted mowing in reverse without worry of a time-out condition.Only when vehicle 12 is shifted out of reverse will the ROS function bedeactivated. Once shifted out of reverse, this mode can only bereinitiated by activating ROS switch 41 before shifting vehicle 12 backinto reverse. The vehicle must be in either neutral or forward toactivate the ROS switch 41. A 2-position ROS switch 41 is indicated inFIG. 2, but a momentary switch or other switch forms could besubstituted. Alternatively, an ROS position can be added to key switch23, thereby eliminating the need for separate ROS switch 41.Additionally, traction controller 51 can be programmed to automaticallyslow vehicle 12 when moving in reverse and/or when mowing in reverse.Audible and/or visual alarms (which may include error codes), objectdetection systems, etc., may also be activated when moving and/or mowingin reverse.

Software switches can be used to slow the vehicle, stop the vehicle orblades automatically, or enable auxiliary functions when certainoperating, alarm, or emergency conditions are met or encountered whileoperating vehicle 12. As an additional safety feature, brake 15 may beconfigured to engage traction drive motor 11 when vehicle 12 is stoppedor stalled. A manual release cable (or other linkage) may be used withbrake 15 to allow the operator to disengage the brake in order to movevehicle 12. The manual release cable may be combined with an integratedswitch in communication with controller 51 to ensure that vehicle 12 isdisabled when moving vehicle 12. Functionally, this gives the operator abypass option to push or tow the vehicle.

The flexible programming capability of mower deck controller 52 drivingthe blades in mower deck 14 allows inclusion of a slight delay and/orramping up to optimal cutting speed for both safety and energyconservation. Another feature that can be implemented is a blade stopfunction that performs a controlled stop of mower blades when either PTOswitch 43 is deactivated or when key switch 23 is deactivated. Forexample, a capacitor in deck controller 52 can latch power so that whenkey switch 23 is switched off before PTO switch 43 is deactivated, mowerdeck controller 52 can back-drive deck motors 27 and 28 to stop mowerblades within a programmed interval instead of allowing them to coast toa stop. For example, this programmed interval may be specified as 5seconds or some other specification corresponding to an industrystandard such as ANSI (American National Standards Institute) or an OEM.(original equipment manufacturer) specification. Controlled braking ofmower blades can also be accomplished by utilizing regenerative brakingor mechanical braking.

Additionally, deck controller 52 may receive a signal from tractioncontroller 51 to stop deck motors 27 and 28 when vehicle 12 has notmoved for a programmed time interval, or if vehicle 12 exceeds aprogrammed maximum travel speed (axle speed sensors, for example, canenable both of these functions), or if other vehicle operationalparameters are exceeded.

Turning now to FIG. 3 (the traction controller 51 state map), variouscombinations of actuator and switch positions define various states fortraction, PTO, ROS, cruise, key switch, sensors and errors whileutilizing operating control system 50 functions as illustrated.Illustrated are 10 different preferred states of operation for tractioncontroller 51 and interrelationships of these states.

The first state 100 is the vehicle OFF state in which vehicle 12 ispowered down and controllers are disabled with key switch 23 in the OFFposition. When key switch 23 is turned to the ON position, controlpasses to state 101, in which traction controller 51 is powered andbegins processing.

State 101 is a diagnostic and preparation to operate state, whichincludes a ready or standing state, if diagnostics pass. If diagnosticsfail, state 101 passes to error state 102 and an alarm is actuated. Anyof the following states described herein can pass to error state 102 ifthey fail any of the conditions outlined for operation within aparticular state. State 101 consists of key switch 23 on, internaldiagnostics pass, PTO switch 43 off, ROS switch 41 off, cruise switch 42off, operator in seat (actuating seat switch 34), foot off acceleratorpedal 40 (in neutral), and manual brake switch 30 off. Also, electricbrake 15 coil resistance is measured to determine presence of the coil.Optionally, the brake holding capacity check, as previously described,may be employed as well. If all of these conditions are met, powercontactor 53 is closed. If the operator then actuates PTO switch 43,control passes to state 110 and the PTO timeout timer is set.Alternatively, if the operator first actuates the accelerator pedal 40,a test of brake 15 is performed. If the brake test is passed, thecontroller 51 passes control to state 103.

State 102 is an error state in which errors can be categorized asrecoverable or non-recoverable. For non-recoverable errors, controlremains in state 102 until key switch 23 is turned off. Recoverableerrors can be resolved without cycling key switch 23 and, when resolved,the alarm is deactivated. Non-recoverable errors occur when thecontroller shuts off the PTO, shuts down the vehicle for not meeting aspecified minimum voltage requirement, a hardware failure is detected, adiagnostic failure occurs, seat switch 43 is detected open in a stateother than state 101 (recoverable error in state 101), or a test ofbrake 15 fails. Recoverable errors may be defined to include, forexample, a condition when the operator is not in the seat, anaccelerator is not in neutral, a manual brake release switch is in an ONposition, etc. Any alarm or emergency condition (for both recoverableand non-recoverable errors) encountered by traction controller 51 ordeck controller 52 will result in passing control to state 102 andstopping of both vehicle 12 and deck 14 blades. If PTO switch 43 was onbefore entering error state 102, it will be necessary to cycle PTOswitch 43 after recovery from the error in order to resume operation ofmower deck 14 motors 27 and 28.

State 103 is a transport state where vehicle 12 is in a travel-onlymode. State 103 consists of key switch 23 on, internal diagnostics pass,PTO switch 43 off, ROS switch 41 on or off, cruise switch 42 on or off,operator in seat (actuating seat switch 34), accelerator pedal 40 ineither forward or reverse and maximum speed enabled. The sequence startswith the operator closing seat switch 34 and then actuating acceleratorpedal 40. A test of brake 15 is performed by traction controller 51 and,if passed, brake 15 is released and electric motor 11 is started in thedirection signaled by the operator's input. If the PTO is activatedwhile in state 103, controller 51 passes control to state 104, 105, 108,or 111, depending on a combination of accelerator pedal 40 position(forward or reverse) and ROS switch 41 position (on or off). If tractioncontroller 51 determines it should pass control to state 105 (attemptedreverse mowing with ROS off), then either vehicle 12 speed is greatlyreduced and mowing is allowed (referenced as “105 Opt 1” in FIG. 3), or,if a reverse cut-off function is selected in the software, then mowingis not allowed (referenced as “105 Opt 2” in FIG. 3) and anon-recoverable error is generated and control passes to state 102. Ifcontrol passes to state 104, 108, or 111, vehicle 12 speed is limited toa programmed forward mowing speed. Cruise switch 42 will only functionif traveling forward and then the speed is maintained while travelingforward. Activating cruise switch 42 while traveling forward “freezes”the actual current vehicle speed. The cruise condition is terminated ifbrake pedal 32 is depressed, or accelerator pedal 40 is moved intoreverse, or accelerator pedal 40 is pressed forward further than the“frozen” position, or cruise switch 42 is actuated while the acceleratorpedal is in neutral. While in cruise mode, if accelerator pedal 40 ispressed forward and cruise switch 42 is actuated again, the “frozen”cruise value will be updated, reflecting the new accelerator position.When accelerator pedal 40 is moved into the neutral position(represented by the PEDAL OFF notations in FIG. 3, as mentionedpreviously), vehicle 12 stops, and when accelerator pedal 40 remains inthe neutral position for a specified, programmed time interval (such as,for example 0.4 seconds), traction controller 51 will return to state101 and engage brake 15. If manual brake switch 30 is activated,controller 51 overrides accelerator pedal 40, forces electric motor 11to zero rpm, stops vehicle 12 and engages brake 15. When operating instate 103, if ROS switch 41 is in the ON position and PTO switch 43 isthen switched to the ON position, traction controller 51 will jump tostate 111 if moving forward and state 108 if moving in reverse.Conversely, if ROS switch 41 is in the OFF position and PTO switch 43 isthen switched to the ON position, traction controller 51 will jump tostate 104 if moving forward and state 105 if moving in reverse.

State 104 is the forward mowing state with ROS off, traveling at areduced working speed. State 104 consists of key switch 23 on, internaldiagnostics pass, PTO switch 43 on, ROS switch 41 off, cruise switch 42on or off, operator in seat (actuating seat switch 34), acceleratorpedal 40 in forward and working speed reduction enabled. Whenaccelerator pedal 40 is moved into the neutral position, vehicle 12stops, and when accelerator pedal 40 remains in the neutral position fora specified, programmed time interval, traction controller 51 jumps tostate 110 and engages brake 15. When PTO switch 43 is switched off,traction controller 51 jumps to state 103 and sends a signal to the deckcontroller 52 (or other auxiliary controller, depending onconfiguration) to stop deck motors 27 and 28. When accelerator pedal 40is moved to the reverse position, control jumps to state 105 and vehicle12 transitions from forward travel to reverse travel, if allowed bysoftware settings. Alternatively, when accelerator pedal 40 is moved tothe reverse position, control jumps to state 105 and then to error state102 if not allowed by software settings. If ROS switch 41 is switchedon, traction controller 51 jumps to state 111. If a momentary ROS switch41 is used (referenced in FIG. 3 as “ROS Opt 2”), the timeout feature isset before transferring to state 111.

State 105 is the attempted reverse mowing with ROS off state. State 105consists of key switch 23 on, internal diagnostics pass, PTO switch 43on, ROS switch 41 off, cruise switch 42 off, operator in seat (actuatingseat switch 34), accelerator pedal 40 in reverse and either a speedreduction function or a cut-off function enabled. Depending on softwaresettings, state 105 either allows mowing in reverse at reduced speedwhen accelerator pedal 40 is in the reverse position (referenced in FIG.3 as “105 Opt 1”), or it does not allow any mowing (referenced in FIG. 3as “105 Opt 2—Reverse Cut-Off”) and control is passed to state 102 andan alarm is generated. If reduced speed mowing is allowed in state 105,the reduced speed may be programmed at, for example, approximately onefoot per second maximum for safety, or other specification correspondingto an industry standard such as ANSI or an OEM specification. If notallowed, and control is passed to state 102 as mentioned above, this isa non-recoverable error, so key switch 23 must be turned off and back onto proceed. ROS switch 41 is disabled while in state 105, so it will notfunction if switched on while in state 105. Under “105 Opt 1”, whenaccelerator pedal 40 is moved to the neutral position, vehicle 12 stops,and when accelerator pedal 40 remains in the neutral position for aspecified, programmed time interval, traction controller 51 jumps tostate 110 and brake 15 is applied. If PTO switch 43 is switched off,control jumps to state 103 and deck motors 27 and 28 are stopped. Ifaccelerator pedal 40 is moved into forward position, traction controller51 jumps to state 104 and vehicle 12 transitions from reverse travel toforward travel.

State 108 is the reverse mowing state with ROS on, operating at areduced working speed. State 108 consists of key switch 23 on, internaldiagnostics pass, PTO switch 43 on, ROS switch 41 on, cruise switch 42off, operator in seat (actuating seat switch 34), accelerator pedal 40in reverse and working speed reduction enabled. When PTO switch 43 isswitched off, traction controller 51 jumps to state 103 and deck motors27 and 28 are stopped. If a latching ROS switch 41 is used (under “ROSOpt 1”), when accelerator pedal 40 is moved into the neutral position,vehicle 12 stops, and when accelerator pedal 40 remains in the neutralposition for a specified, programmed time interval, traction controller51 jumps to state 110 and brake 15 is applied. If accelerator pedal 40is moved into forward position, traction controller 51 jumps to state104 (under “ROS Opt 1”) and vehicle 12 transitions from reverse travelto forward travel. If a momentary ROS switch is used (under “ROS Opt2”), when accelerator pedal 40 is moved to the neutral position, vehicle12 stops, and when accelerator pedal 40 remains in the neutral positionfor a specified, programmed time interval, traction controller 51 jumpsto state 112 and brake 15 is applied. If accelerator pedal 40 is movedinto forward position, traction controller 51 jumps to state 111 (under“ROS Opt 2”) and vehicle 12 transitions from reverse travel to forwardtravel.

State 110 is a temporary, stationary vehicle state with PTO switch 43 onand ROS switch 41 off State 110 consists of key switch 23 on, internaldiagnostics pass, PTO switch 43 on, ROS switch 41 off, cruise switch 42off, operator in seat (actuating seat switch 34), accelerator pedal 40in neutral, working speed reduction enabled and electric brake 15applied. When the PTO timeout has elapsed, PTO switch 43 is switched offby the software and traction controller 51 jumps to state 101. Ifaccelerator pedal 40 is moved into the forward position, tractioncontroller 51 will jump to state 104 or, if moved into the reverseposition, to state 105. If ROS switch 41 is switched on, tractioncontroller 51 will jump to state 112. If a momentary ROS switch 41 isused (“ROS Opt 2”), traction controller 51 sets the ROS timeout timerbefore transfer to state 112.

State 111 is the forward mowing state with ROS on (and which enables atimeout function for the ROS under “ROS Opt 2”). State 111 consists ofkey switch 23 on, internal diagnostics pass, PTO switch 43 on, ROSswitch 41 on, cruise switch 42 on or off, operator in seat (actuatingseat switch 34), accelerator pedal 40 in forward and working speedreduction enabled. If accelerator pedal 40 is moved into reverseposition, traction controller 51 jumps to state 108 and vehicle 12transitions from forward travel to reverse travel. When PTO switch 43 isswitched off, traction controller 51 jumps to state 103 and deck motors27 and 28 are stopped. When accelerator pedal 40 is moved to the neutralposition, vehicle 12 stops, and when accelerator pedal 40 remains in theneutral position for a specified, programmed time interval, tractioncontroller 51 jumps to state 112 and brake 15 is applied. If ROS switch41 is switched off, traction controller 51 jumps to state 104. If amomentary ROS switch 41 is used (“ROS Opt 2”), and if the ROS timeoutelapses, controller 51 jumps to state 104.

State 112 is a temporary, stationary vehicle state with ROS switch 41and PTO switch 43 both on (and which enables a timeout function for theROS under “ROS Opt 2”). State 112 consists of key switch 23 on, internaldiagnostics pass, PTO switch 43 on, ROS switch 41 on, cruise switch 42off, operator in seat (actuating seat switch 34), accelerator pedal 40in neutral and working speed reduction enabled. When the PTO timeoutelapses, traction controller 51 jumps to state 101 and deck motors 27and 28 are stopped. If accelerator pedal 40 is moved into the forwardposition, traction controller 51 will jump to state 111 or, if movedinto the reverse position, to state 108. If ROS switch 41 is switchedoff, traction controller 51 jumps to state 110. If a momentary ROSswitch 41 is used (“ROS Opt 2”), and if the ROS timeout elapses,controller 51 jumps to state 110.

Turning now to FIG. 4 (the deck controller 52 state map), variouscombinations of actuator and switch positions define various states forthe PTO, key switch and errors while utilizing operating controllersystem functions as illustrated. Illustrated are 5 different states ofoperation for deck controller 52 and the interrelationships of thesestates.

State 100, as previously described above, is the vehicle OFF state inwhich vehicle 12 is powered down and controllers are disabled with keyswitch 23 in the OFF position. When key switch 23 is switched on, andafter diagnostics have passed, deck controller 52 is enabled bycontroller 51 and deck control passes to state 202.

In state 202, deck controller 52 is enabled with key switch 23 on andPTO switch 43 off When PTO switch 43 is switched on, deck controller 52jumps to state 203.

In state 203, deck controller 52 is enabled with key switch 23 on andPTO switch 43 on to power mower deck motors 27 and 28. From state 203,deck controller 52 transfers control to one of two possible states,error state 204 or PTO disabled state 205.

State 204 is the error state which is entered if one or more deck motors27 and 28 are outside the programmed allowable temperature, current, orvoltage range. Once the error is removed, operator cycling of PTO switch43 once (after a programmed delay of approximately 5 to 10 seconds toprevent overheating of MOSFETs or other sensitive electronic components)will return control to state 203 and start deck motors 27 and 28 runningagain. If key switch 23 is placed in the OFF position while in state204, deck controller 52 will jump to state 100.

In state 205, the PTO is disabled. Mower deck 14 cutting blades arestopped (within a programmable time limit governed by industry standardsor OEM specifications for safety) by pulse width modulation (PWM)control of deck motors 27 and 28. When PTO switch 43 is switched off(thereby removing the PTO ground), deck controller 52 jumps to state 202from state 205. If PTO switch 43 is switched back on and the groundsignal is reapplied at state 205 before the motor stopping function iscompleted, deck controller 52 returns to state 203. If the key remainsoff in state 205, deck controller 52 returns to state 100.

FIGS. 1 and 2 illustrate some of the various inputs that may beconnected via operator-actuated switches to traction controller 51.Traction controller 51 as illustrated allows an operator to use anemergency stop switch 31, brake switch 30, or the key switch 23 OFFposition to initiate engagement of fail-safe brake 15 on electric motor11. Cruise switch 42 can be engaged to maintain a constant travel speedinput which is cancelled upon receiving a brake pedal 32 or acceleratorpedal 40 input signal outside a set or programmed range. If the setrange is exceeded, cruise switch 42 must be turned off and back on againto reactivate the cruise function. As mentioned previously, a separateF-N-R switch may be added if rocker style accelerator pedal 40 (shown)is replaced by a different type of accelerator pedal. Optionally,hand-operated lever or joystick controls may be used in lieu of pedal(s)and steering wheel.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof

1. A computer-readable medium having computer-executable instructionsfor performing steps for a control process for an electric drive systemof a vehicle having at least one electric drive motor, at least oneelectric auxiliary motor, at least one drive controller, and at leastone sensor, the steps comprising: receiving one or more signals fromeither one or both of the at least one sensor and the at least one drivecontroller; receiving a signal from the drive controller indicating thatthe vehicle has been stopped for a predetermined period of time; andstopping the electric auxiliary motor if the vehicle has been stoppedfor a predetermined period of time.
 2. A computer-readable medium havingcomputer-executable instructions for performing steps for a controlprocess for an electric drive system of a vehicle having at least oneelectric drive motor, at least one electric auxiliary motor, at leastone drive controller, and at least one sensor, the steps comprising:receiving one or more signals from either one or both of the at leastone sensor and the at least one drive controller; receiving a signalfrom the drive controller indicating that a speed of the vehicle hasexceeded a predetermined speed; and stopping the electric auxiliarymotor if the speed of the vehicle has exceeded the predetermined speed.3. A computer-readable medium having computer-executable instructionsfor performing steps for a control process for an electric drive systemof a vehicle having at least one electric drive motor and at least onesensor, the steps comprising: determining whether the vehicle is in astart-up mode; driving the electric drive motor to a predeterminedholding torque specification while a vehicle brake is engaged;monitoring whether a drive wheel of the vehicle moves; and disablingdriving of the at least one drive motor if one or more drive wheels ofthe vehicle move.
 4. A computer-readable medium havingcomputer-executable instructions for performing steps for a controlprocess for an electric drive system of a vehicle having at least oneelectric drive motor, at least one electric auxiliary motor, at leastone drive controller, and at least one sensor, the steps comprising:monitoring a load on the at least one electric auxiliary motor;determining if a predetermined load on the at least one electricauxiliary motor has been exceeded; and decreasing a speed of the atleast one electric drive motor when the predetermined load on the atleast one electric auxiliary motor has been exceeded.